A-LevelBiologyNucleic acids and protein synthesis9700/22 · Oct/Nov 2021 · Q516 Marks

The causative organism of measles is Morbillivirus. Young children who have not been vaccinated for measles are at highest risk of becoming ill and of developing complications associated with the disease.

(a)The genetic material of Morbillivirus is a strand of RNA. Statements A, B and C relate to the structure of RNA. State the correct term or terms to match each of statements A to C. A The names of the two purines and two pyrimidines in RNA. purines pyramidines B The type of covalent bond between RNA nucleotides. C The pentose sugar of the RNA nucleotide.[4]
(b)Describe how measles is transmitted.[3]
(c)(i)Inhaled tobacco smoke passes through the larynx (voice box) and other structures in the gas exchange system to reach the alveoli. Complete Fig. 5.1 to list, in the correct sequence, the main structures of the gas exchange system through which the tobacco smoke passes to reach the alveoli. larynx alveoli [Figure 5.1][1]
(c)(ii)State the short-term effects of carbon monoxide on the cardiovascular system.[2]
(d)(i)State the trend shown in Fig. 5.2 between 2000 and 2017. [Figure 5.2: Graph showing estimates of number of deaths from measles globally, 2000-2017][1]
(d)(ii)Suggest reasons for the trend shown in Fig. 5.2.[3]
(e)A child with leukaemia is at high risk of developing measles even though the child has a high white blood cell count and has been vaccinated against the disease. Explain why this child is at high risk of developing measles.[2]

This question uses a diagram from the original paper, which isn't shown here. Open the full paper from the past papers archive to see it.

Mark scheme

Marking points from the official mark scheme (Oct/Nov 2021). The mark or mark type is shown in brackets.

[4] ignore single letters for the bases
A purines = adenine and guanine ; in either order
pyrimidines = cytosine and uracil ; in either order
B phosphodiester (bond) ;
C ribose ;
[3] any three from: penalise once if incorrect, pathogen / type of organism
aerosol infection / droplet infection / ref. to airborne droplets ;
in context of droplets containing, pathogen / virus
infected person, exhales / expires / breathes out / coughs / sneezes / AW, (airborne droplets) ;
(airborne droplets) breathed in / AW, by, uninfected / healthy, person;
idea of transmitted when uninfected person touches an infected surface and puts fingers into, mouth / nose ;
R contact without qualification
[1] trachea
bronchus / bronchi
bronchiole / bronchioles ; A types of bronchiole
[2] A CO for carbon monoxide A Hb / hb, for haemoglobin
any two from
1 forms carboxyhaemoglobin ; A binds to haemoglobin (permanently)
2 less haemoglobin available to bind oxygen / haemoglobin has higher affinity for carbon monoxide (than for oxygen) ;
3 reduces, percentage saturation of haemoglobin (with oxygen) / AW ; A less, oxygen binds to haemoglobin / oxyhaemoglobin forms I prevents oxygen binding
if mp2 and mp3 not gained allow one mark for statements such as reduces capacity for binding of oxygen to hb / less oxygen carried by hb / decreases the oxygen carrying capacity of hb
4 decreased quantity of oxygen transported / AW ;
5 damages, endothelium / tunica intima / lining of blood vessels ;
[1] (steady) increase in number of (estimated) deaths (from measles, over time / from 2000 to 2017) ;
A (relatively) constant then (steady) increase in number of (estimated deaths over time)
[3] any three from: I ref. to cost or mutations
1 as (global) population increased, higher, number / proportion, of unvaccinated ; ora
2 ref. to HIV link to measles ; e.g. increase in number of people living with HIV increases spread of measles increase in cases of HIV/AIDS, measles can be an opportunistic disease R spread of HIV / AIDS weakened immune system in people with HIV/AIDS so measles more likely to occur (in unvaccinated)
3 less / no, herd immunity (so increased chance of getting measles) ; A ref. to larger, number / proportion, unvaccinated will increase risk of spreading disease context is community
4 one example of a difference between unvaccinated versus vaccinated ; e.g. risk of death from measles is higher in unvaccinated unvaccinated do not have, (artificial active) immunity / memory cells context is individuals
5 suggestion as to why fewer people are vaccinated ; e.g. reluctance, of parents to get child vaccinated reluctance because of, cultural / religious, beliefs difficulty in obtaining vaccine in context of remote communities collapse of vaccination programmes in some countries / AW lack of, trained trained professionals / health facilities, to deliver vaccine lack of education about benefits of vaccine / AW
6 suggestion as to why measles cases (and so deaths) may increase ; e.g. (greater proportion of people) malnourished / lack vitamin A (greater proportion of people) living in, overcrowded / poor, conditions I overcrowded countries measles is easily spread (with increase in population) A very infectious measles is more easily spread in overcrowded conditions
7 example of spread (of measles) owing to movement of people between countries ; e.g. (unvaccinated) people with measles arriving to a country and spreading disease unvaccinated people travelling to countries with the disease, catching measles and taking it back home people arriving with measles to countries with low vaccination rates
8 AVP ; e.g. ref. to, no / any specific difficulty for, contact tracing lack of, isolation / quarantining poor epidemiological records so authorities cannot react to outbreaks improved, recording / reporting, of deaths over the time period
[2] any two from:
(high count owing to), cancerous / uncontrolled mitosis of, white blood cells ; A malignant cells A uncontrolled division
white blood cells (in child with leukaemia) cannot, function (in immunity) / protect / example of function ; A undifferentiated / unspecialised
(so) weakened immune system (and more likely of developing measles) ; AW
vaccination is, less effective / not effective / gives weak immune response ;
secondary immune response, does not occur / too slow (after vaccination);
AVP ; has memory cells but clonal expansion, does not occur / is faulty